Electric power is generally transmitted from generation plants to end consumers (industries, corporations, homeowners, etc.) via a transmission and distribution grid consisting of a network of power stations, transmission circuits, and substations interconnected by power-lines. Once at the end consumers, electricity can be used to power any number of devices.
With the advent of Smart Grid technologies, there is more focus on enabling protection and control in the distribution feeders and extending communications down to feeder devices. Electric utilities use medium voltage feeder lines to distribute energy to neighborhood transformers. Often, the physical electrical network may look like a graph with an open loop wherein the two ends of the loop are feeders connected to primary substations. Utilities designate places in the electrical network where the loop should be open while ensuring that electricity is supplied to all of their customers. In order to reduce the impact of a fault, typically utilities add automation devices such as reclosers, sectionalizers, and/or switches on the feeders. This helps contain the impact of the fault to a given segment of the feeder.
When the grid detects a fault (high current rush) on a feeder/line from a substation it acts promptly to protect itself by opening switches on the faulty line in order to cut off the high current. As a result, all customers on that feeder lose power until the fault location is identified, the faulty segment is isolated, and power is restored to customers whose electricity can be provided through routes which do not include the faulty segment.
In order for a distribution automation (DA) device (such as a circuit breaker/recloser controller) to function properly, the correct relay operating curve needs to be configured. This curve helps configure the sensitivity of the relay towards fault current (i.e., the time for which a fault current should be seen before the relay triggers and isolates the circuit). Relay operating characteristics (e.g., over current curves) today are manually configured to provide correct relay coordination, the goal being correct discrimination, i.e., each one must select and isolate only the faulty section of the power system network, leaving the rest of the system undisturbed. An important note about the relay operating characteristic and other relay configuration parameters, however, is that they are dependent on the circuit configuration, and in the case of reconfiguration (e.g., due to a fault or manual changes) need to be reconfigured depending on the new feeder configuration. The more complex the topology of a feeder circuit is, therefore, the more complex a task it is to manually configure these parameters.